1. Field of the Invention
The invention pertains to the field of internal combustion engines. More particularly, the invention pertains to the integration of variable cam timing controls into the engine""s front cover.
2. Description of Related Art
Internal combustion engines have become increasingly complex, as features such as variable cam timing (VCT) and active noise cancellation are included. For example, using VCT, the angular displacement, or phase of a camshaft, relative to the crankshaft to which it is drivably connected, is dynamically altered to bring about changes in engine characteristics, such as fuel economy or power. Typically, there is a feedback loop in which the desired values of such engine characteristics are measured against their existing values, and changes are effected inside the engine in response to discrepancies. To accomplish this, modern automobiles usually have a control module (or more than one) having a microcomputer that constantly analyzes data fed into it from various parts of the engine and other parts of the automobile and ambient conditions (exhaust gas sensors, pressure and temperature sensors, etc.) and emits signals in response to such data. For example, in regard to VCT, as changes occur in engine and external conditions, the angular displacement between the cam shaft and the crank shaft that drives it is altered.
The conventional method of connecting a system, such as a VCT system, to the control module is to run a set of wires from each solenoid, valve, actuator or motor and each sensor back to the engine controller. As a result, the number of wires feeding into the engine controller has recently become unmanageable. For example, some engine controllers now have upwards of 150 to 200 externally-connected wires. With such increased complexity of engines, it is becoming more difficult for the engine controller to manage all of the features, due to their fast update rate and fast computational speed requirements.
Various attempts have been made to address the problem of managing such increased engine complexity. For example, U.S. Pat. No. 5,353,755 to Matsuo et al. discloses a variable valve timing control system incorporated into the front cover of a V-type internal combustion engine. The patent teaches a V-type engine comprising a plurality of hydraulically actuated valve operation mode control actuators for two cylinder banks. A hydraulic fluid network is fluidly disposed between a main gallery of the cylinder block and the plurality of hydraulically actuable valve operation mode control actuators, and includes a single control valve, which is common to all of the hydraulically actuable valve operation mode control actuators. This control valve is attached to a casing adapted to receive a drive system connecting the engine camshafts to the engine crankshaft. The casing also has internal passages forming a part of the hydraulic fluid network between the control valve and the plurality of hydraulically actuable valve operation mode control actuators. However, the prior art does not teach incorporation of VCT sensors or the VCT control unit into the front engine cover.
It will be understood by one skilled in the art that in the context of this invention the term xe2x80x9cfront coverxe2x80x9d refers to the cover over the timing components of the enginexe2x80x94the camshaft drive element(s) (gear, sprocket or pulley) and cam phaser(s), the crankshaft end and drive element (gear, sprocket or pulley), and the power transmission component (chain, belt or gears) connecting the crankshaft drive to the cam drive(s). In the traditional fore-and-aft engine mounting, this cover would usually be toward the front of the engine (hence the term, xe2x80x9cfront coverxe2x80x9d), but it will be understood that in other engine mounting schemes it might be toward the side of the car (as in a transverse engine) or facing the rear.
A front cover for an internal combustion engine comprises variable cam timing (VCT) controls integrated into the cover, including variable force solenoids (VFS) and cam (and possibly crankshaft) position sensors, the cover being located in front of and operably connected to a cam phaser. A VCT control module, also mounted on the cover, communicates with the actuators and sensors, and provides the connection to the car""s control module, thus limiting the number of external conductors necessary to interface with the VCT system. In one embodiment of the invention, the engine cover, once assembled, comprises a single unit having an electronic interface module (EIM), VFS and position sensor integrated within said cover. This invention allows the cam position sensor to sense the cam position from a wheel mounted in front of the cam phaser, rather than from a pulse wheel mounted on the cam.